Sorry I have nothing to add here but I'd like to ask a question.
What type of VPN are you using? I have been using VPNs for 5 years with various ISPs and have never encountered any problems with latency and jitter. For the past couple of years I keep 5 VPN tunnels up to different sites 24x7. The only problems I have encountered is with out of order packets. I am curious what VPNs have problems and why.